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The visual system IV
The visual cortices
The primary visual pathway
From perret-optic.ch
Primary vision
Structure of the primary visual cortexThe headquartes
Information flow
Intra V1
1
Higher areas
2/3
Intra V1
4a
Higher areas
4b
4cα
4cβ
M
P
5
Superior colliculus, pulvinar, pons
6
LGN, thalamic interneurons
Visual columnsRFs and orientations
200 μm
Orientation map
How does orientation selectivity
arise?
Ferster et al. (1996), Reid & Alonso (1996)
Receptive fields in different cortical
layers
Layers IV and VI
Simple cells
Layers II and III
Complex cells
Are complex cells more complex,
or just more active?
Complex cell!
Adapted from Kandel et al. (2000)
Are complex cells more complex,
or just more active?
Crowder et al. (2007)
Higher visual areas:
The Where and What
Magnocellular!
Parvocellular!
Higher visual areas:
Inferotemporal cortex
Fusiform face area
Halle Berry Cells
Halle
Berry
Contour perception is fed back to V1
Lamme (1995)
Higher visual areas:
The Where and What
Magnocellular!
Parvocellular!
Motion perception is fed back to V1
Muckli et al. (2005)
Summary IV –
The visual cortex…
• continues the segregation in magno- and parvocellular
pathway as the Where and What pathway
•is segregated into six layers, all of which fulfill different
tasks in coordinating activity from the thalamus, other
cortical areas and the brain stem
• is organized in response preference columns, according to
ocular dominance, stimulus orientation, contrast, length
etc.
• contains neurons with simple and complex responses
•is in constant feedback-feedforward loops with the Where
and the What pathways